1. Field of the Invention
The present invention relates to an SLR camera using light-sensitive film or an electronic image pick-up device so that object images can be taken as latent images on the light-sensitive film or as digital images using the image pick-up device, which can be stored in a recording medium such as a floppy disk or a flash memory.
2. Description of the Related Art
Roll-film SLR cameras using an interchangeable film back which are designed so that different types of film (e.g., 70 mm wide filmxe2x80x94either 120 or 220 roll-film, negative film or positive film) can be selectively used are known. In this type of camera, if the sensitive surface of an image pick-up device (e.g., a CCD image sensor) can be properly positioned in a focal plane in camera body, the camera can be used as digital camera. Accordingly, a digital back has been proposed in which an image pick-up device (e.g., a CCD image sensor) is provided, instead of a light-sensitive film, so that the camera can be used as a digital camera when the digital back is attached to the camera body.
The digital back must be provided in front of the image pick-up device thereof with a filter group which includes, e.g., a filter for filtering infrared rays, a low-pass filter, a protection glass for protecting the image pick-up device from dust and/or other filter or filters. On the other hand, it is necessary for an exposed front surface (light-sensitive surface) of a strip of film to be positioned in a focal plane formed through the photographic lens when the film back is attached to the camera body. Due to this conventional structure, if the digital back is attached to the camera body instead of the film back, it is difficult to arrange the sensitive surface of the image pick-up device to be positioned in the focal plane. This is because the sensitive surface of the image pick-up device needs to be positioned behind the focal plane by a distance corresponding to the total thickness of the aforementioned filter group positioned in front of the image pick-up device so as to prevent the filter group from interfering with the focal plane shutter provided in the camera body. If the sensitive surface of the image pick-up device is simply arranged to be positioned in the focal plane, the aforementioned filter group will definitely interfere with the focal plane shutter provided in the camera body. If the protection glass is formed so as to be extremely thin, while the other filter or filters of the filter group are positioned between the focal plane shutter and the photographic lens, such a problem is eliminated in theory. However, this is impractical.
The same problem occurs in not only roll-film SLR cameras using the interchangeable film back, but also in conventional SLR cameras having a focal plane shutter, in the case where an digital back cover (i.e., an openable back cover having an image pick-up device therein) instead of a film back cover is rotatably coupled to the back of the camera body via a hinge. Namely, the aforementioned filter group positioned in front of the image pick-up device of the digital back cover likewise interferes with the focal plane shutter of the camera body.
An object of the present invention is to provide an SLR camera which can be selectively used as a conventional SLR camera using light-sensitive film, or as a digital camera using an image pick-up device, wherein the aforementioned filter group, which is positioned in front of the image pick-up device provided in a digital back or digital back cover, does not interfere with the focal plane shutter when the camera is used as a digital camera.
The present invention has been made based on an idea of using an interchangeable lens provided therein with a lens shutter (a diaphragm shutter, bladed lens shutter) while prohibiting the focal plane shutter of the camera body from operating as a shutter when the SLR camera is used as a digital camera, and another idea of providing the SLR camera with a device for preventing the image pick-up device from interfering with the focal plane shutter of the camera body.
SLR cameras according to the present invention are generally classified into two types: a first type wherein either a film back or a digital back is selectively attached to the camera body, and a second type wherein a film back cover or a digital back cover is selectively rotatably coupled to the back of the camera body. These two types substantially have the common mechanical structure but are controlled in different manners.
In order to achieve the above mentioned object, an SLR camera system is provided, including a camera body having a focal plane shutter; an interchangeable lens detachably attached to the camera body, the interchangeable lens including a lens shutter; a film back and a digital back which are selectively attached to the camera body, the film back accommodating a light-sensitive film which is to be positioned, upon the attachment thereof to the camera body, at a focal plane located in the camera body, the digital back including an image pick-up device, and the image pickup device having a sensitive surface which is positioned at the focal plane upon the attachment of the digital back to the camera body; a drive mechanism, provided in the digital back, which drives the image pick-up device in a direction of an optical axis of the interchangeable lens; and a controller which controls the focal plane shutter, the lens shutter, and the drive mechanism when the digital back and the interchangeable lens are attached to the camera body. When the digital back and the interchangeable lens are attached to the camera body, upon receiving a shutter release signal, the controller controls the focal plane shutter to fully open and subsequently controls the drive mechanism to advance the image pick-up device so as to move the sensitive surface thereof to the focal plane before controlling the lens shutter to operate, and wherein the controller controls the drive mechanism to retreat the image pick-up device and subsequently controls the focal plane shutter to shut after controlling the lens shutter to operate.
The drive mechanism can include, for example, at least one feed screw for moving the image pick-up device in the direction of the optical axis, and a drive motor for rotating the at least one feed screw in forward and reverse directions.
Preferably, the drive mechanism includes a position detector for detecting the position of the image pick-up device, and at least one stopper which prevents the image pick-up device from advancing further when the sensitive surface has moved to the focal plane. The controller cuts off power supply to the drive motor before the sensitive surface reaches the focal plane in accordance with the detection of the position detector, when the image pick-up device is driven to advance by the drive mechanism.
According to another aspect of the present invention, a camera body is provided, including a focal plane shutter; an interchangeable lens detachably attached to the camera body, the interchangeable lens including a lens shutter; a film back and a digital back which are selectively attached to the camera body, the film back accommodating a light-sensitive film which is to be positioned, upon the attachment thereof to the camera body, at a focal plane located in said camera body, the digital back including an image pick-up device, and the image pick-up device having a sensitive surface which is positioned at the focal plane upon the attachment of the digital back to the camera body; a drive mechanism, provided in the digital back, which drives the image pick-up device in a direction of an optical axis of the interchangeable lens; and a controller which controls the focal plane shutter, the lens shutter, and the drive mechanism when the digital back and the interchangeable lens are attached to the camera body. The controller controls the focal plane shutter to fully open and subsequently controls the drive mechanism to advance the image pick-up device so as to move the sensitive surface thereof to the focal plane immediately after the interchangeable lens and the digital back are attached to the camera body. The controller controls the drive mechanism to retreat the image pick-up device and subsequently controls the focal plane shutter to shut when the digital back is detached from the camera body.
The drive mechanism can include, for example, at least one feed screw for moving the image pick-up device in the direction of the optical axis; and a drive motor for rotating the at least one feed screw in forward and reverse directions.
Preferably, the drive mechanism includes a position detector for detecting the position of the image pick-up device, and at least one stopper which prevents the image pick-up device from advancing further when the sensitive surface has moved to the focal plane. The controller cuts off power supply to the drive motor before the sensitive surface reaches the focal plane in accordance with the detection of the position detector, when the image pick-up device is driven to advance by the drive mechanism.
According to another aspect of the present invention, an SLR camera system is provided, including a camera body having a focal plane shutter; an interchangeable lens detachably attached to the camera body, the interchangeable lens including a lens shutter; a film back and a digital back which are selectively attached to the camera body, the film back accommodating a light-sensitive film which is to be positioned, upon the attachment thereof to said camera body, at a focal plane located in said camera body, the digital back including an image pick-up device, and the image pick-up device having a sensitive surface which is positioned at the focal plane upon the attachment of the digital back to the camera body; a drive mechanism, provided in the digital back, which drives the image pick-up device in a direction of an optical axis; and a controller which controls the focal plane shutter so as to fully open, and subsequently controls the drive mechanism to advance the image pick-up device so as to move the sensitive surface thereof to the focal plane immediately after the interchangeable lens and the digital back are attached to the camera body.
According to another aspect of the present invention, an SLR camera system is provided, including a camera body including a focal plane shutter, a hinge, a film back cover which can be coupled to the hinge so as to be openable about the hinge, and a pressure device for pressing against a light-sensitive film in the area of a film frame to keep the light-sensitive film flat thereat; a digital back cover which can be coupled to the hinge instead of the film back cover so as to be openable about the hinge, the digital back cover including an image pick-up device, wherein a sensitive surface of the image pick-up device is to be positioned at a focal plane located in the camera body; a back-cover detector, wherein in the case where the digital back cover is coupled to the hinge, when the digital back cover is rotated about the hinge from an open state to a closed state, the back-cover detector detects a position wherein the focal plane shutter needs to be opened in order to prevent the sensitive surface of the image pick-up device from interfering with the focal plane shutter; an interchangeable lens detachably attached to the camera body and including a lens shutter; and a controller which controls the focal plane shutter when the digital back cover and the interchangeable lens are attached to the camera body. In the case where the digital back cover is coupled to the hinge, when the digital back cover is rotated about the hinge from the open state to the closed state, the controller controls the focal plane shutter to fully open so as to allow the sensitive surface of the image pick-up device to move to the focal plane immediately after the back-cover detector detects the above-mentioned position, and when the digital back cover is rotated about the hinge from the closed state to the open state, the controller controls the focal plane shutter to shut immediately after the back-cover detector detects the above-mentioned position.
Preferably, the interchangeable lens further includes an iris diaphragm.
The image pick-up device can be, for example, a CCD image sensor.
In an embodiment, the digital back further includes a filter group fixedly positioned in front of the image pick-up device.
The back-cover detector can include, for example, a projection which is formed integral with the digital back cover, and a switch, provided in the camera body, which is turned ON and OFF when the projection of the digital back cover presses against and withdraws from the switch, respectively.
The present disclosure relates to subject matter contained in Japanese Patent Applications No.11-141199 (filed on May 21, 1999) and No.11-279892 (filed on Sep. 30, 1999) which are expressly incorporated herein by reference in their entireties.